Android: find the id of the inflated buttons

Question

I have inflated buttons using the following codes, and would like to swap the location of the 2 buttons selected using simple TranslateAnimation.

Codes:

    for (int k = 1; k <= quotient; k++) 
    {
        LinearLayout.LayoutParams params3 = new LinearLayout.LayoutParams(button_width,row_height);
        params3.setMargins(button_margin, button_margin, button_margin, button_margin);
        btn_right = new Button(this);
        btn_right.setId(idd);
        final int id_ = btn_right.getId();
        btn_right.setText(""+question[idd]);

        frame_row.addView(btn_right, params3);

        btn_right.setOnClickListener(new View.OnClickListener() 
        {
            public void onClick(View view) 
            {                       
                btn_right = ((Button) findViewById(id_));
                X1 = getRelativeLeft(btn_right);
                Y1 = getRelativeTop(btn_right);
                int b = Integer.parseInt(""+btn_right.getText().toString());
                selection ++;
                if (selection%2 ==1)
                {
                    selected_id1 = id_;
                    selected_color1 = b;                        
                    custom_toast("X1=" +X1 + "\nY1=" + Y1);                                             
                }
                else
                {
                    selected_id2 = id_;
                    selected_color2 = b;
                    X2 = getRelativeLeft(btn_right);
                    Y2 = getRelativeTop(btn_right);

                    custom_toast("X2=" +X2 + "\nY2=" + Y2);

                    // the first one 
                    btn_right = ((Button) findViewById(selected_id1));
                    anim1=new TranslateAnimation(0, (X2-X1), 0, (Y2-Y1)); 
                    anim1.setFillAfter(true);
                    anim1.setDuration(animationTime);
                    anim1.setAnimationListener(Game.this);  
                    btn_right.startAnimation(anim1);

                    // the second one
                    btn_right = ((Button) findViewById(selected_id2));
                    anim2=new TranslateAnimation(0, (X1-X2), 0, (Y1-Y2));
                    anim2.setFillAfter(true);
                    anim2.setDuration(animationTime);
                    anim2.setAnimationListener(Game.this);
                    btn_right.startAnimation(anim2);                                
                }

@Override
public void onAnimationEnd(Animation animation) 
{

    if (animation == anim1)
    {           
        custom_toast("1 clear");
        btn_right = ((Button) findViewById(selected_id1));
        btn_right.clearAnimation();     // Line 426

    }
    if (animation == anim2)
    {           
        custom_toast("2 clear");
        btn_right = ((Button) findViewById(selected_id2));
        btn_right.clearAnimation();     
    }
}

Logcat:

04-21 21:28:00.728: E/AndroidRuntime(11341): java.lang.NullPointerException
04-21 21:28:00.728: E/AndroidRuntime(11341):    at com.abc.abc.Game.onAnimationEnd(Game.java:426)

Question:

For info, if selection%2 ==1, it means user has only pressed the first button and is not yet ready for swap, and hence to record the id and its X, Y coordinates. If selection%2 ==0, it means user has pressed 2 buttons and is ready to swap after recording the 2nd's X and Y.

Also, the (X1, Y1) and (X2, Y2) coordinates are reporting correctly.

It runs into a NPE at line 426 btn_right.clearAnimation(); (as specified above) . My question is, since all the buttons are inflated, and I have already setId for all the inflated buttons, why it would still runs out as a NPE at line 426, or actually how should I specify the 2 buttons that the user has touched so as to implement the swapping animation?

Thanks!!

Answer 1

create a list of buttons, you can create buttons and set their id, tags and onclicklistenners like this and add them to the button list:

 buttonList = new ArrayList<Button>();

    for (int i=0;i<2;i++){
        Button button = new Button(getApplicationContext());
        button.setOnClickListener(customListenner);
        button.setAnimation(anim);
        button.setId(i);
        button.setTag(i);
        myLayout.addView(button);
        buttonList.add(button);
    }

and when you need to use the button again, just call with their id or tags from the list. (buttonList.get(0).getId())

If you need different listenners, you can control them by using the unique tag check in if function and declare another action.

This is the method that I always use when I need to create and use animations on dynamic views programmatically.